Callers of Notification::Dismiss() assume that the notification
instance is not deleted after the call, but this was not the case
for LibnotifyNotification:
- Destroy() would get `this` deleted.
- notify_notification_close() in portal environment triggers
LibnotifyNotification::OnNotificationClosed(), and finally calls
Destroy()
This patch removes all Destroy() in Dismiss(), and adds a boolean
to tell whether notify_notification_close() is running, to avoid crash
under portal environment.
Fixes#40461.
4f76fff978